At least 74 opinions, memoranda, and letters issued by the Justice Department’s Office of Legal Counsel (OLC) between 2002 and 2009 on core post-9/11 national security topics, including intelligence activities and the detention and interrogation of terrorist suspects, remain entirely classified, according to a new report by the Brennan Center for Justice at NYU School of Law. OLC’s advice is legally binding on the executive branch in the same way a court order would be.

OLC opinions are just one component of an unprecedented buildup of secret law created by the federal government since 9/11 through a range of unpublished legal rules and opinions – all issued without public scrutiny or input – that govern policies affecting the lives and liberties of U.S. citizens.

Relying partly on new data obtained through Freedom of Information Act requests, the Brennan Center’s report, The New Era of Secret Law, concludes that secret law is prevalent throughout all three branches of government. Along with OLC opinions, the report examines classified rulings of the Foreign Intelligence Surveillance Court (known as the “FISA Court”), secret presidential directives, unpublished regulations, redacted opinions in regular federal courts, agreements with foreign nations, closed immigration proceedings, and even classified provisions of legislation.

Sen. Ron Wyden (D-Or.), a longtime critic of secret law and its corrosive effect on democracy, hailed the report: “Secret law has been the root cause of most of the biggest intelligence scandals of the past fifteen years. This report presents a detailed yet readable analysis of the problem, from foundational questions to recent history. As author Elizabeth Goitein notes, ‘The objections to secret law should be articulated, not assumed.’ This report ably articulates the many problems with secret law, and proposes concrete, workable reforms.”

“Secret law undermines the democratic process, the rule of law, and our constitutional system of checks and balances,” said author Elizabeth Goitein, co-director of the Brennan Center’s Liberty & National Security Program. “When small groups of government officials create law outside the public eye, that law is less likely to reflect the will of the people, and it’s more likely to be in tension with the published law. National security may sometimes require keeping operational details secret, but the law itself can and should be public.”

Among our findings:

Secret OLC Memos: Between 1998 and 2013, one out of every five OLC opinions was classified and therefore unavailable to the public. At least 74 opinions, memoranda, and letters issued between 2002 and 2009 on several of the most important legal topics arising after 9/11 – including detention, interrogation, intelligence activities and intelligence-sharing, the United States’ response to terrorism, and the law of armed conflict – remain entirely classified.

Secret Courts: In the wake of Edward Snowden’s disclosures, FISA Court opinions have become much more transparent, and many “historical” opinions have been declassified and released. Nonetheless, 25-30 opinions and orders that were issued between mid-2003 and mid-2013 and deemed “significant” by the Attorney General remain entirely classified, while at most 19 opinions from this time period that could be considered “significant” have been made public. In other words, the majority of significant pre-Snowden FISA case law remains secret.

Secret International Agreements: According to State Department documents obtained by the Brennan Center in litigation, the United States entered into 807 secret “congressional-executive” agreements with foreign nations between 2004 and 2014 – 42 percent of all the international agreements the U.S. executed during this time period. These have the same legal force as treaties and often concern matters vital to the security and economic well-being of Americans, but they may remain unpublished on national security grounds.

The Brennan Center’s report puts forth specific recommendations for reforms to limit the extent and impact of secret law, including raising the standards for classifying legal rules or interpretations; requiring secrecy decisions to be made by an inter-agency panel rather than single official; publishing an index of secret laws including certain basic information about each law; and establishing firm limits for how long law may remain secret.